SpringBoot : 解决Long类型在前端JS中失去精度的问题

HttpMessageConverter

相信使用过Spring的开发人员都用过@RequestBody、@ResponseBody注解，可以直接将输入解析成Json、将输出解析成Json，但HTTP 请求和响应是基于文本的，意味着浏览器和服务器通过交换原始文本进行通信，而这里其实就是HttpMessageConverter发挥着作用。
HttpMessageConverter
Http请求响应报文其实都是字符串，当请求报文到java程序会被封装为一个ServletInputStream流，开发人员再读取报文，响应报文则通过ServletOutputStream流，来输出响应报文。
从流中只能读取到原始的字符串报文，同样输出流也是。那么在报文到达SpringMVC / SpringBoot和从SpringMVC / SpringBoot出去，都存在一个字符串到java对象的转化问题。这一过程，在SpringMVC / SpringBoot中，是通过HttpMessageConverter来解决的。HttpMessageConverter接口源码：

public interface HttpMessageConverter<T> {
    boolean canRead(Class<?> var1, @Nullable MediaType var2);
    boolean canWrite(Class<?> var1, @Nullable MediaType var2);
    List<MediaType> getSupportedMediaTypes();
    T read(Class<? extends T> var1, HttpInputMessage var2) throws IOException, HttpMessageNotReadableException;
    void write(T var1, @Nullable MediaType var2, HttpOutputMessage var3) throws IOException, HttpMessageNotWritableException;
}

FastJson

代码

@Configuration
public class WebMvcConfig implements WebMvcConfigurer {
    @Override
    public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
         converters.add(new ByteArrayHttpMessageConverter());
        // @ResponseBody 解决乱码
        converters.add(new StringHttpMessageConverter(StandardCharsets.UTF_8));
        converters.add(new ResourceHttpMessageConverter());
        converters.add(new AllEncompassingFormHttpMessageConverter());
        converters.add(fastJsonHttpMessageConverter());
    }
    @Bean
    public FastJsonHttpMessageConverter fastJsonHttpMessageConverter() {
        FastJsonHttpMessageConverter converter = new FastJsonHttpMessageConverter();
        FastJsonConfig config = new FastJsonConfig();
        //Long类型转String类型
        SerializeConfig serializeConfig = SerializeConfig.globalInstance;
        // ToStringSerializer 是这个包 com.alibaba.fastjson.serializer.ToStringSerializer
        serializeConfig.put(BigInteger.class, ToStringSerializer.instance);
        serializeConfig.put(Long.class, ToStringSerializer.instance);
        serializeConfig.put(Long.TYPE, ToStringSerializer.instance);
        config.setSerializeConfig(serializeConfig);
        config.setSerializerFeatures(
                SerializerFeature.WriteMapNullValue, // 保留map空的字段
                SerializerFeature.WriteNullStringAsEmpty, // 将String类型的null转成""
                SerializerFeature.WriteNullNumberAsZero, // 将Number类型的null转成0
                SerializerFeature.WriteNullListAsEmpty, // 将List类型的null转成[]
                SerializerFeature.WriteNullBooleanAsFalse, // 将Boolean类型的null转成false
                SerializerFeature.WriteDateUseDateFormat,  //日期格式转换
                SerializerFeature.DisableCircularReferenceDetect // 避免循环引用
        );
        config.setSerializeFilters(valueFilter);
        converter.setFastJsonConfig(config);
        converter.setDefaultCharset(StandardCharsets.UTF_8);
        // 解决中文乱码问题，相当于在Controller上的@RequestMapping中加了个属性produces = "application/json"
        List<MediaType> mediaTypeList = new ArrayList<>();
        mediaTypeList.add(MediaType.APPLICATION_JSON);
        converter.setSupportedMediaTypes(mediaTypeList);
        return converter;
    }
}
   /**
     * FastJson过滤器将null值转换为字符串
     * obj 是class
     * s 是key值
     * o1 是value值
     */
    public static final ValueFilter valueFilter = (obj, s, v) -> {
        if (v == null) {
            return "";
        }
        return v;
    };

代码2

@Configuration
public class WebMvcConfig implements WebMvcConfigurer {
    /**
     * 添加拦截器
     */
    @Override
    public void addInterceptors(InterceptorRegistry registry){
        //全局拦截器
        registry.addInterceptor(new GlobalInterceptor())
                .addPathPatterns("/**")
                .excludePathPatterns("/static/**");
        //登陆拦截器
        registry.addInterceptor(new LoginInterceptor())
                .addPathPatterns("/**")
                .excludePathPatterns("/static/**");
    }
    /**
     * 利用fastJson替换掉jackson，且解决中文乱码问题
     */
    @Override
    public void configureMessageConverters(List<HttpMessageConverter<?>> converters){
        FastJsonHttpMessageConverter fastConverter = new FastJsonHttpMessageConverter();
        FastJsonConfig fastJsonConfig = new FastJsonConfig();
        fastJsonConfig.setSerializerFeatures(
                SerializerFeature.DisableCircularReferenceDetect,
                SerializerFeature.WriteMapNullValue,
                SerializerFeature.WriteNullNumberAsZero,
                SerializerFeature.WriteNullStringAsEmpty,
                SerializerFeature.WriteNullListAsEmpty,
                SerializerFeature.WriteNullBooleanAsFalse,
                SerializerFeature.WriteNonStringKeyAsString,
                SerializerFeature.BrowserCompatible);
        //解决Long转json精度丢失的问题
        SerializeConfig serializeConfig = SerializeConfig.globalInstance;
        serializeConfig.put(BigInteger.class, ToStringSerializer.instance);
        serializeConfig.put(Long.class, ToStringSerializer.instance);
        serializeConfig.put(Long.TYPE, ToStringSerializer.instance);
        fastJsonConfig.setSerializeConfig(serializeConfig);
        //处理中文乱码问题
        List<MediaType> fastMediaTypes = new ArrayList<>();
        fastMediaTypes.add(MediaType.APPLICATION_JSON_UTF8);
        fastConverter.setSupportedMediaTypes(fastMediaTypes);
        fastConverter.setFastJsonConfig(fastJsonConfig);
        converters.add(fastConverter);
    }
}

Jackjson

@EnableWebMvc
@Configuration
public class WebConfig  extends WebMvcConfigurerAdapter {
    public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
        MappingJackson2HttpMessageConverter jacksonConverter = new MappingJackson2HttpMessageConverter();
        SimpleModule simpleModule = new SimpleModule();
        simpleModule.addSerializer(Long.class, ToStringSerializer.instance);
        simpleModule.addSerializer(Long.TYPE, ToStringSerializer.instance);
        ObjectMapper objectMapper = new ObjectMapper();
        objectMapper.registerModule(simpleModule);
        jacksonConverter.setObjectMapper(objectMapper);
        converters.add(jacksonConverter);
    }
}

@Component
public class JacksonSerializerConfig {
    @Bean
    public Jackson2ObjectMapperBuilderCustomizer jackson2ObjectMapperBuilderCustomizer() {
        Jackson2ObjectMapperBuilderCustomizer customizer = new
            Jackson2ObjectMapperBuilderCustomizer() {
            @Override
            public void customize(Jackson2ObjectMapperBuilder jacksonObjectMapperBuilder) {
                jacksonObjectMapperBuilder
                    .serializerByType(Long.class, ToStringSerializer.instance)
                    .serializerByType(Long.TYPE, ToStringSerializer.instance);
            }
        };
        return customizer;
    }
}

参考

• 链接